Joe Biden sworn in as U.S. President

Democrat Joe Biden has been sworn-in as the 46th President of the United States.

With his hand on an heirloom Bible that has been in his family for more than a century, Biden took the presidential oath of office administered by U.S. Chief Justice John Roberts, vowing to "preserve, protect and defend the Constitution of the United States."

Biden, 78, became the oldest U.S. president in history at a scaled-back ceremony in Washington that was largely stripped of its usual pomp and circumstance, due both to the coronavirus and security concerns following the January 6 assault on the U.S. Capitol by supporters of outgoing President Donald Trump.

The norm-defying Trump flouted one last convention on his way out of the White House when he refused to meet with Biden or attend his successor's inauguration, breaking with a political tradition seen as affirming the peaceful transfer of power.

Trump, who never conceded the November 3 election, did not mention Biden by name in his final remarks as president on Wednesday morning, when he touted his administration's record and promised to be back "in some form."

He boarded Air Force One for the last time and headed to his Mar-a-Lago retreat in Florida.

Top Republicans, including Vice President Mike Pence and the party's congressional leaders, attended Biden's inauguration, along with former U.S. Presidents Barack Obama, George W. Bush and Bill Clinton.

Biden's running mate, Kamala Harris, the daughter of immigrants from Jamaica and India, became the first Black person, first woman and first Asian American to serve as vice president after she was sworn in by U.S. Supreme Court Justice Sonia Sotomayor, the court's first Latina member.

Biden takes office at a time of deep national unease, with the country facing what his advisers have described as four compounding crises: the pandemic, the economic downtown, climate change and racial inequality. He has promised immediate action, including a raft of executive orders on his first day in office.